Trouble with parsing _TABLE_SUFFIX in Bigquery #1

Hi,

First, big thanks for making this! It really makes a world of a difference.

I used pybigquery for Superset, a data viz tool from Airbnb. When I have DATETIME(TIMESTAMP(PARSE_DATE('%Y%m%d',_TABLE_SUFFIX))) AS dt, it works fine in SQL lab. But when I try to visualize, i get this error unsupported format character 'Y' (0x59) at index 111. Is there anyway around this?

I tried adding '%' to '%Y%m%d' but no luck.

Link to superset: https://github.com/apache/incubator-superset